More than 100 people are reported to have been killed in the Syrian city of Aleppo after a fresh attack by forces loyal to President Bashar al-Assad.

Several residential areas in Syria's largest city have been bombed by warplanes in an attempt to crush the rebels. The pro-government forces are using aerial bombardment as a first wave of attack, followed up by ground assaults.

The attacks were prompted by a rebel offensive which captured an army barracks in the district of Hananou, and have been concentrated on neighbourhoods which have fallen into anti-government hands.

In an apparent response to the attacks by pro-government troops, two powerful bombs exploded in Aleppo targeting a hospital which has been turned into a makeshift barracks of the Syrian army. The rebels say they used locals to plant the bombs, and the attacks have killed or wounded nearly 100 soldiers.

"The army had taken over the neighbourhood and emptied it from residents. The hospital was turned into army barracks," activist Ahmad Saeed told Reuters.

The fresh wave of conflict comes after an attack by pro-government troops destroyed a water main, leaving thousands without water.